The invention relates to a centrifugal separator having hydraulically operated outlet valves, for the concentration of suspended solids, said valves being uniformly distributed about the circumference of the drum in the plane of the greatest drum diameter, passages for carrying the operating liquid extending through the floor of the drum, said valves having movable valve bodies protected against the pressure of the drum charge, closing nozzle apertures at the periphery of the drum by centrifugal force at full rotatory drum speed and being displaced radially towards the drum axis during operation by means of an operating liquid and thereby releasing nozzle apertures for the emergence of the concentrate.
A centrifugal separator of this kind is known, for example, from German Utility Model 75 27 869.
Centrifugal separators of this type of construction are used for the concentration of solids which are of a soft, e.g. yeasty, consistency, but also for the concentration of solids of greater specific weight, which are preferably spun out through nozzles located at a relatively great distance from the drum axis, normally at the periphery of the drum, and the content of solids in the suspension can vary greatly. Furthermore, it must be possible for the solid material to be raised to a very high concentration.
The nozzles disposed at the periphery of the drum for the emergence of the concentrate are opened whenever the movable valve bodies in the valves are moved radially toward the drum axis. The timing of the valve openings can be automatically controlled through a control apparatus on the basis of the emerging concentrate or of the emerging clear phase. It is disadvantageous in this system that valve operating water must be fed to the valves during the entire open period if the valves are to remain open for a relatively long time. The consumption of valve operating water in this case is very great.
To remedy these disadvantages, the valve seats or the movable valve bodies have been provided with calibrated passages or slits, a certain amount of concentrate being carried off continually, and the valve bodies being opened completely only at certain intervals of time.
A disadvantage of this last-named construction is, however, that the calibrated passages or slits have to be adapted to the smallest flow of concentrate that is to be expected, and thus the necessity exists of keeping the nozzles and slits very small, but thereby creating the danger of rapid clogging if the solid particles are larger in diameter than the calibrated bores or slits.